Scientific Summary · Compiled by Brian Gaillard
Brian Gaillard
Hybrid athlete and applied nutrition enthusiast at Nutrition•pro
There are dozens of supplements that promise weight loss. Most have never been rigorously tested, a few have been for 20 years. This summary compiles 18 meta-analyses published between 2003 and 2024 (Obesity Reviews, BMJ, JAMA, Cochrane, Am J Clin Nutr) covering over 250 randomized clinical trials and 25,000 participants, to answer a simple question: which supplements produce a real statistical signal, and which ones are just noise?
Our approach
Executive Summary
The aggregation of 18 independent meta-analyses produces a stable ranking.
No supplement replaces a calorie deficit. But four molecules emerge with solid evidence to produce clinically measurable weight loss (>1 kg vs placebo over 12 weeks): glucomannan, green tea (catechins + caffeine), berberine and soluble fiber such as psyllium. The best-selling supplements (garcinia, raspberry ketone, green coffee) show weak or non-significant effects in rigorous trials.
1. Placebo vs Supplement: What Remains After Filtering
In clinical trials, two groups are compared: one takes the molecule, the other a placebo. Both lose weight (motivation, associated dietary monitoring). What matters is the difference between the two bars.
2. Level of evidence: not all signals are equal
An effect measured in 3 trials in 140 people does not carry the same weight as an effect confirmed in 40 trials in 4,000 people. The GRADE scale measures the strength of the signal.
3. The final weighted ranking
We combine the observed effect, evidence level, and tolerability into an overall score. A supplement that is effective but poorly tolerated remains poorly ranked.
Supplements that survive the meta-analytical filter are those that help maintain a dietary plan (satiety, thermogenesis, absorption), not those that claim to burn fat. The ranking simply reflects this logic.
4. Top 4 supplements with solid signal
1. Glucomannan (Konjac) — −2.1 kg vs placebo / 12 weeks (Onakpoya 2014). Soluble fiber extracted from Konjac root. It swells up to 100 times its volume in the stomach and increases satiety. Only supplement for which EFSA validated the health claim "contributes to weight loss as part of a calorie-restricted diet" (EU Reg. 432/2012).
2. Green tea (EGCG catechins + caffeine) — −1.3 kg vs placebo / 12 weeks (Hursel 2009, Phung 2010, Jurgens 2012). 40 trials compiled, over 4,000 participants. Slightly increases energy expenditure and fat oxidation. Synergistic effect with caffeine, more pronounced in non-habitual consumers.
3. Berberine — −1.5 kg vs placebo / 12 weeks (Lan 2015, Asbaghi 2020). Alkaloid that activates AMPK like metformin. Effect particularly pronounced in subjects with metabolic syndrome or prediabetes. Moderate tolerance (frequent digestive issues at high doses).
4. Soluble fibers (psyllium, β-glucan) — −1.2 kg vs placebo / 12 weeks (Salas-Salvado 2017). 62 trials, over 3,800 participants. Slow carbohydrate absorption, increase satiety, improve lipid profile. Well-documented mechanism, modest but consistent effect.
5. Supplements to avoid or take with caution
Garcinia cambogia. Modest effect in the very short term that disappears in quality trials. Documented cases of toxic hepatitis (Crescioli 2018), ANSES safety recommendations in 2019. Score 2.1/10.
Chromium picolinate. Effect less than 0.5 kg vs placebo, not clinically significant. Useful only in case of proven deficiency. Score 3.5/10.
Green coffee. Apparently strong effect but based on 3 trials and 140 people, with significant industry bias. The meta-analysis authors themselves conclude that "the quality of existing trials is too low to draw definitive conclusions."
Raspberry ketones, L-carnitine, forskoline, spirulina. No robust evidence in humans for weight loss.
Methodology
This synthesis is an umbrella review : 18 meta-analyses published in peer-reviewed journals (Obesity Reviews, BMJ, JAMA, NEJM, Cochrane, Am J Clin Nutr) between 2003 and 2024 were aggregated. Supplements are ranked according to three weighted criteria: effect size (40%), GRADE evidence level (35%), tolerance and safety (25%).
Inclusion criteria: meta-analysis including ≥ 3 RCTs, adult population with overweight or obesity, minimum duration 8 weeks, comparison vs placebo (not vs another active intervention), PRISMA method or equivalent.
Important limitations: the placebo effect in weight loss is significant (often 1 to 2 kg over 12 weeks), which brings the performance of many supplements close to statistical noise. The majority of trials are industry-funded, which introduces recognized bias. Finally, the supplements tested are taken in addition to a dietary intervention: the net effect of "supplement alone" is probably lower.
- Onakpoya I et al. (2014). Glucomannan for weight loss: a systematic review and meta-analysis of randomized controlled clinical trials. British Journal of Nutrition, 111(7):1175-1182.
- Mhurchu CN et al. (2005). Chitosan for overweight or obesity. Cochrane Database Syst Rev, (3):CD003892.
- Hursel R et al. (2009). The effects of green tea on weight loss and weight maintenance: a meta-analysis. International Journal of Obesity, 33:956-961.
- Phung OJ et al. (2010). Effect of green tea catechins with or without caffeine on anthropometric measures. American Journal of Clinical Nutrition, 91(1):73-81.
- Jurgens TM et al. (2012). Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database Syst Rev, (12):CD008650.
- Onakpoya I et al. (2011). The use of green coffee extract as a weight loss supplement. Gastroenterology Research and Practice, 2011:382852.
- Onakpoya I et al. (2010). The use of Garcinia extract (hydroxycitric acid) as a weight loss supplement. Journal of Obesity, 2011:509038.
- Heymsfield SB et al. (1998). Garcinia cambogia (hydroxycitric acid) as a potential antiobesity agent: a randomized controlled trial. JAMA, 280(18):1596-1600.
- Lan J et al. (2015). Meta-analysis of the effect and safety of berberine in the treatment of type 2 diabetes mellitus, hyperlipemia and hypertension. Phytomedicine, 22(3):415-431.
- Asbaghi O et al. (2020). The effects of berberine supplementation on cardiovascular risk factors in adults. Complementary Therapies in Medicine, 50:102410.
- Pittler MH et al. (2003). Chromium picolinate for reducing body weight: meta-analysis of randomized trials. International Journal of Obesity, 27:522-529.
- Onakpoya I et al. (2013). Chromium supplementation in overweight and obese: a systematic review and meta-analysis. Obesity Reviews, 14:496-507.
- Whigham LD et al. (2007). Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. American Journal of Clinical Nutrition, 85(5):1203-1211.
- Whiting S et al. (2012). Capsaicinoids and capsinoids: a potential role for weight management? Appetite, 59(2):341-348.
- Janssens PL et al. (2013). Acute effects of capsaicin on energy expenditure and fat oxidation in negative energy balance. PLoS ONE, 8(7):e67786.
- Salas-Salvadó J et al. (2017). Effect of consumption of dietary fiber on body weight: a systematic review and meta-analysis. Advances in Nutrition, 8(6):901-912.
- Egras AM et al. (2011). An evidence-based review of fat modifying supplemental weight loss products. Journal of Obesity, 2011:297315.
- Akhlaghi M et al. (2020). The effect of curcumin on weight loss and weight maintenance. Phytotherapy Research, 34(11):2872-2882.
Brian Gaillard
Nutrition and Performance Author
Hybrid athlete for over 10 years: weight training, running, swimming, HIIT and muay thai. Brian selects, compiles and contextualizes recent scientific literature on sports nutrition and weight loss for NUTRITION•PRO editorial content. Each synthesis is based on meta-analyses and clinical trials filtered according to their level of evidence, combined with experience accumulated through his training sessions and exchanges with coaches and nutritionists.
